LXR linux-old/lib/zlib_inflate/inffast.c

   1/* inffast.c -- process literals and length/distance pairs fast
   2 * Copyright (C) 1995-1998 Mark Adler
   3 * For conditions of distribution and use, see copyright notice in zlib.h 
   4 */
   5
   6#include <linux/zutil.h>
   7#include "inftrees.h"
   8#include "infblock.h"
   9#include "infcodes.h"
  10#include "infutil.h"
  11#include "inffast.h"
  12
  13struct inflate_codes_state;
  14
  15/* simplify the use of the inflate_huft type with some defines */
  16#define exop word.what.Exop
  17#define bits word.what.Bits
  18
  19/* macros for bit input with no checking and for returning unused bytes */
  20#define GRABBITS(j) {while(k<(j)){b|=((uLong)NEXTBYTE)<<k;k+=8;}}
  21#define UNGRAB {c=z->avail_in-n;c=(k>>3)<c?k>>3:c;n+=c;p-=c;k-=c<<3;}
  22
  23/* Called with number of bytes left to write in window at least 258
  24   (the maximum string length) and number of input bytes available
  25   at least ten.  The ten bytes are six bytes for the longest length/
  26   distance pair plus four bytes for overloading the bit buffer. */
  27
  28int zlib_inflate_fast(bl, bd, tl, td, s, z)
  29uInt bl, bd;
  30inflate_huft *tl;
  31inflate_huft *td; /* need separate declaration for Borland C++ */
  32inflate_blocks_statef *s;
  33z_streamp z;
  34{
  35  inflate_huft *t;      /* temporary pointer */
  36  uInt e;               /* extra bits or operation */
  37  uLong b;              /* bit buffer */
  38  uInt k;               /* bits in bit buffer */
  39  Bytef *p;             /* input data pointer */
  40  uInt n;               /* bytes available there */
  41  Bytef *q;             /* output window write pointer */
  42  uInt m;               /* bytes to end of window or read pointer */
  43  uInt ml;              /* mask for literal/length tree */
  44  uInt md;              /* mask for distance tree */
  45  uInt c;               /* bytes to copy */
  46  uInt d;               /* distance back to copy from */
  47  Bytef *r;             /* copy source pointer */
  48
  49  /* load input, output, bit values */
  50  LOAD
  51
  52  /* initialize masks */
  53  ml = zlib_inflate_mask[bl];
  54  md = zlib_inflate_mask[bd];
  55
  56  /* do until not enough input or output space for fast loop */
  57  do {                          /* assume called with m >= 258 && n >= 10 */
  58    /* get literal/length code */
  59    GRABBITS(20)                /* max bits for literal/length code */
  60    if ((e = (t = tl + ((uInt)b & ml))->exop) == 0)
  61    {
  62      DUMPBITS(t->bits)
  63      *q++ = (Byte)t->base;
  64      m--;
  65      continue;
  66    }
  67    do {
  68      DUMPBITS(t->bits)
  69      if (e & 16)
  70      {
  71        /* get extra bits for length */
  72        e &= 15;
  73        c = t->base + ((uInt)b & zlib_inflate_mask[e]);
  74        DUMPBITS(e)
  75
  76        /* decode distance base of block to copy */
  77        GRABBITS(15);           /* max bits for distance code */
  78        e = (t = td + ((uInt)b & md))->exop;
  79        do {
  80          DUMPBITS(t->bits)
  81          if (e & 16)
  82          {
  83            /* get extra bits to add to distance base */
  84            e &= 15;
  85            GRABBITS(e)         /* get extra bits (up to 13) */
  86            d = t->base + ((uInt)b & zlib_inflate_mask[e]);
  87            DUMPBITS(e)
  88
  89            /* do the copy */
  90            m -= c;
  91            if ((uInt)(q - s->window) >= d)     /* offset before dest */
  92            {                                   /*  just copy */
  93              r = q - d;
  94              *q++ = *r++;  c--;        /* minimum count is three, */
  95              *q++ = *r++;  c--;        /*  so unroll loop a little */
  96            }
  97            else                        /* else offset after destination */
  98            {
  99              e = d - (uInt)(q - s->window); /* bytes from offset to end */
 100              r = s->end - e;           /* pointer to offset */
 101              if (c > e)                /* if source crosses, */
 102              {
 103                c -= e;                 /* copy to end of window */
 104                do {
 105                  *q++ = *r++;
 106                } while (--e);
 107                r = s->window;          /* copy rest from start of window */
 108              }
 109            }
 110            do {                        /* copy all or what's left */
 111              *q++ = *r++;
 112            } while (--c);
 113            break;
 114          }
 115          else if ((e & 64) == 0)
 116          {
 117            t += t->base;
 118            e = (t += ((uInt)b & zlib_inflate_mask[e]))->exop;
 119          }
 120          else
 121          {
 122            z->msg = (char*)"invalid distance code";
 123            UNGRAB
 124            UPDATE
 125            return Z_DATA_ERROR;
 126          }
 127        } while (1);
 128        break;
 129      }
 130      if ((e & 64) == 0)
 131      {
 132        t += t->base;
 133        if ((e = (t += ((uInt)b & zlib_inflate_mask[e]))->exop) == 0)
 134        {
 135          DUMPBITS(t->bits)
 136          *q++ = (Byte)t->base;
 137          m--;
 138          break;
 139        }
 140      }
 141      else if (e & 32)
 142      {
 143        UNGRAB
 144        UPDATE
 145        return Z_STREAM_END;
 146      }
 147      else
 148      {
 149        z->msg = (char*)"invalid literal/length code";
 150        UNGRAB
 151        UPDATE
 152        return Z_DATA_ERROR;
 153      }
 154    } while (1);
 155  } while (m >= 258 && n >= 10);
 156
 157  /* not enough input or output--restore pointers and return */
 158  UNGRAB
 159  UPDATE
 160  return Z_OK;
 161}
 162